Assume the RRA protocol is in use. How long should servers retain unacknowledged reply data?
Should servers repeatedly send the reply in an attempt to receive an acknowledgement?

What will be an ideal response?

The timeout period for storing a reply message is the maximum time that it is likely for any client to a re
transmit a request message. There is no definite value for this, and there is a trade-off between safety and buffer
space. In the case of RRA, reply messages are generally discarded before the timeout period has expired
because an acknowledgement is received. Suppose that a server using RRA re-transmits the reply message
after a delay and consider the case where the client has sent an acknowledgement which was late or lost. This
requires (i) the client to recognise duplicate reply messages and send corresponding extra acknowledgements
and (ii) the server to handle delayed acknowledgments after it has re-transmitted reply messages. This possible
improvement gives little reduction in storage requirements (corresponding to the occasional lost
acknowledgement message) and is not convenient for the single threaded client which may be otherwise
occupied and not be in a position to send further acknowledgements.